1. Field of the Invention
The present invention relates to a reclining device for use in an automotive seat and, more particularly, to such reclining device which is capable of arranging a seat back level with a seat cushion when the seat back is inclined back horizontally and also which eliminates the possibility that the lower end portion of the seat back may rub against the back and bottom of an occupant when the angle of inclination of the seat back is altered.
2. Description of the Prior Art
Conventionally, a general type of reclining device, as shown in FIG. 1, is mounted to a seat so as to extend between the respective side surfaces of a seat cushion (A) and a seat back (B). In such reclining device, the main parts of the reclining device are packaged in a united body and the united body is fixed to the seat cushion by bolts (103)(103) or similar fasteners, while a rotary member such as an arm (104) or the like provided in the seat back (B) is rotatably mounted to the seat cushion at a position located upwardly of the above-mentioned fixed position of the united body.
In other words, because the rotary member (104) of the seat back (B) must be mounted to the seat cushion (A) in such a manner that it can be rotated up to substantially 180 degrees relative to the seat cushion (A), the rotary member (104) of the seat back (B) must be located above the mounting positions of the bolts (103)(103), that is, the positions in which the reclining device is fixed to the seat cushion (A). Thus, the mounting portion (105) of the rotary member (104) to the seat cushion (A) becomes the center of rotation of the seat back (B).
Therefore, since the center of rotation of the seat back (B) is disposed at a position higher than the seat cushion (A), when the seat back (B) is inclined back horizontally, there is produced a difference in level between the seat cushion (A) and the seat back (B), (that is, the seat back (B) is situated higher than the seat cushion (A)).
In FIG. 1, reference numeral (101) designates an upper rail of a seat adjuster fixed to the seat cushion (A), and (102) a lower rail of the same fixed to the floor of an automotive seat.
Also, since this conventional reclining device is adapted such that the seat back can only be inclined back and forth, the center of rotation of the seat back is greatly away from the point of the occupant's hips, that is, a point corresponding the center of rotation of a man's body between the trunk and the thigh of the body. For this reason, each time the seat back is inclined, the lower end portion of the seat back is caused to rub against the back and bottom of the occupant, so that the occupant must re-sit to avoid such uncomfortable rubbing.
In view of the above-mentioned circumstances, the present application has developed an improved reclining device which can eliminate the above-mentioned drawbacks and has disclosed it in Japanese Patent Publication No. 70713 of 1981. In this reclining device, a movable arm to be fixed to a seat back is rotatably connected to a base plate to be fixed to a seat cushion via a link piece and a sector, and the four points of connection thereof are used to form a trapezoidal link mechanism. Also, the center of rotation of the movable arm is made to substantially correspond to a center of rotation between the seat back and the seat cushion.
However, since this reclining device employs the trapezoidal-node-type reclining mechanism, it is complicated in structure and the whole device is large in size. Therefore, when the reclining device is mounted to the outer surfaces of the seat back and seat cushion, the appearance of the seat may be impaired.
Also, the conventional general type of reclining device is mounted to the seat so as to extend across the outer side surfaces of the seat back and seat cushion after the seat is completed.
Therefore, since the reclining device is exposed out on the outer surface of the seat, the appearance of the seat is impaired, and there must be formed in frames, cushion members and the like which form the seat back mounting holes for fixing the reclining device. Further, since these mounting holes are covered with a trim cover assembly, when the reclining device is mounted to the seat, the mounting position of the reclining device cannot be observed from outside, which results in the increased number of man-hour.